Graphical Turbulence Guidance (GTG)
performance statistics
This page shows statistical performance of GTG for the past 12 months
and is updated quarterly. Two types of plots are included:
1) a
discrimination plot that measures the trade-offs between
correctly classifying positive pilot reports of turbulence versus
mis-classifying pilot reports of "negative
turbulence;" 2) an airspace coverage
plot that measures the trade-offs between correctly classifying
positive pilot reports of turbulence versus the amount of airspace
impacted by the forecasts. The skill index (SI)
is related to the area under the curve for the discrimination plot and
ranges from 0 to 100. The forecasts have positive skill if SI is
greater than 50; larger values of SI indicate greater skill. Note that
airspace is defined as the total volume, from 20,000 to 42,000
ft, covered by a Yes GTG forecast. GTG forecasts are issued at 1200,
1500, 1800, and 2100 UTC; forecasts with lead times of 3, 6, 9, and 12
hours and valid time between 1500 and 0000 UTC are included in the
analyses.
In both types of plots, lines located closer to the
upper-left corner represent better forecasts because better
forecasts capture a larger proportion of the positive turbulence
reports while simultaneously covering a smaller proportion of airspace
and making fewer mis-diagnoses of the "negative turbulence"
reports. The graphics below show the overall annual performance
statistics, followed by statistics for each of the four seasons.
Additional details
on the statistical procedures used to create these graphics are
available.